Electrosurgical apparatus with retractable blade

ABSTRACT

An electrosurgical apparatus with a retractable blade for use in cold plasma applications, electrosurgical cutting and mechanical cutting is provided. The electrosurgical apparatus employs a tip of the retractable blade as a sharp conductive point to generate a plasma beam or discharge. When the blade is retracted within the electrosurgical apparatus, it is electrically energized while an inert gas flows over it, producing a cold plasma discharge. In the de-energized state, the blade is advanced and used as a traditional, mechanical surgical blade.

PRIORITY

This application claims priority on U.S. Provisional Patent Appl. No.61/411,174, filed Nov. 8, 2010, entitled “ELECTROSURGICAL APPARATUS WITHRETRACTABLE BLADE”, the content of which is hereby incorporated byreference in its entirety.

BACKGROUND

Field. The present disclosure relates generally to electrosurgery andelectrosurgical systems and apparatuses, and more particularly, to anelectrosurgical apparatus with a retractable blade for use in coldplasma applications, electrosurgical cutting and mechanical cutting.

Description of the Related Art. High frequency electrical energy hasbeen widely used in surgery. Tissue is cut and bodily fluids arecoagulated using electrosurgical energy.

Electrosurgical instruments generally comprise “monopolar” devices or“bipolar” devices. Monopolar devices comprise an active electrode on theelectrosurgical instrument with a return electrode attached to thepatient. In monopolar electrosurgery, the electrosurgical energy flowsthrough the active electrode on the instrument through the patient'sbody to the return electrode. Such monopolar devices are effective insurgical procedures where cutting and coagulation of tissue are requiredand where stray electrical currents do not pose a substantial risk tothe patient.

Bipolar devices comprise an active electrode and a return electrode onthe surgical instrument. In a bipolar electrosurgical device,electrosurgical energy flows through the active electrode to the tissueof a patient through a short distance through the tissue to the returnelectrode. The electrosurgical effects are substantially localized to asmall area of tissue that is disposed between the two electrodes on thesurgical instrument. Bipolar electrosurgical devices have been found tobe useful with surgical procedures where stray electrical currents maypose a hazard to the patient or where other procedural concerns requireclose proximity of the active and return electrodes. Surgical operationsinvolving bipolar electrosurgery often require methods and proceduresthat differ substantially from the methods and procedures involvingmonopolar electrosurgery.

Gas plasma is an ionized gas capable of conducting electrical energy.Plasmas are used in surgical devices to conduct electrosurgical energyto a patient. The plasma conducts the energy by providing a pathway ofrelatively low electrical resistance. The electrosurgical energy willfollow through the plasma to cut, coagulate, desiccate, or fulgurateblood or tissue of the patient. There is no physical contact requiredbetween an electrode and the tissue treated.

Electrosurgical systems that do not incorporate a source of regulatedgas can ionize the ambient air between the active electrode and thepatient. The plasma that is thereby created will conduct theelectrosurgical energy to the patient, although the plasma arc willtypically appear more spatially dispersed compared with systems thathave a regulated flow of ionizable gas.

Atmospheric pressure discharge cold plasma applicators have found use ina variety of applications including surface sterilization, hemostasis,and ablation of tumors. In the latter example, the process can berelatively slow, generate large volumes of noxious smoke with vaporizedand charred tissue, and may cause collateral damage to surroundinghealthy tissue when high power electrosurgical energy is used. Precisionaccuracy can also be a problem, due to the width of the plasma beam.

Often, a simple surgical knife is used to excise the tissue in question,followed by the use of a cold plasma applicator for cauterization,sterilization, and hemostasis. An improved approach would have bothfacilities in the same surgical tool.

SUMMARY

The present disclosure relates to an electrosurgical apparatus with aretractable blade for use in cold plasma applications, electrosurgicalcutting and mechanical cutting. The advancement of this new approach isto use the tip of the retractable blade as the sharp conductive point togenerate the plasma beam or discharge. When the blade is retractedwithin the electrosurgical apparatus, it is electrically energized whilean inert gas flows over it, producing a cold plasma discharge. In thede-energized state, the blade is advanced and used as a traditionalsurgical blade. In a third state, the blade is advanced and used whileboth electrically energized and with inert gas flow. This third stateresembles an electrosurgical knife approach, however, with the additionof the inert gas flow, cuts made show virtually no eschar, with verylittle collateral damage along the side walls of the cut. Furthermore,the cutting speed is considerably faster, with less mechanical cuttingresistance as compared to when the knife blade is not electricallyenergized. Hemostasis is also affected during this process.

In one aspect of the present disclosure, an electrosurgical apparatus isprovided including a housing having a passage extending therethough, thehousing having a proximal end and a distal end; an electricallyconducting tube having a proximal end and a distal end, the electricallyconducting tube being disposed in the passage of the housing; aninsulating outer tube having a proximal end and a distal end, the outertube disposed around the electrically conducting tube with the proximalend of the outer tube coupled to the distal end of the housing, theelectrically conducting tube being movable along a longitudinal axis ofthe housing and outer tube; and an electrically conducting blade coupledto the distal end of the electrically conducting tube, wherein in afirst position of the electrically conducting tube, the blade extendsbeyond the distal end of the outer tube for mechanical cutting and, in asecond position of the electrically conducting tube, the blade isretracted within the outer tube and is energized via the electricallyconducting tube to form plasma when an inert gas flows through theelectrically conducting tube, wherein the electrically conducting tubeis configured as a structural current limiting capacitor to limitcurrent applied to a operative site when the electrically conductingtube is energized.

In another aspect, the electrically conducting tube includes a first,inner flow tube having a proximal end and a distal end; a second, outerflow tube having a proximal end and a distal end; and a cylindricalinsulator disposed around the distal end of the first, inner flow tubefor coupling the first, inner flow tube to an inner portion of theproximal end of the second, outer flow tube, wherein an overlappingportion of the first, inner flow tube, the cylindrical insulator and thesecond, outer flow tube forms the structural current limiting capacitor.

In a further aspect, at least one of the first, inner flow tube andsecond, outer flow tube is movable relative to each other to varying acapacitance value of the structural current limiting capacitor.

In another aspect, the electrosurgical apparatus includes a first slidermember coupled to the first, inner flow tube for variably setting acurrent limit of the capacitor, the first slider member being accessibleon the housing.

In yet another aspect, the electrosurgical apparatus includes a secondslider member coupled to the second, outer flow tube for extending andretracting the blade, the second slider member being accessible on thehousing.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is an illustration of an exemplary monopolar electrosurgicalsystem in accordance with an embodiment of the present disclosure;

FIG. 2A is a schematic diagram of an electrosurgical apparatus inaccordance with an embodiment of the present disclosure;

FIG. 2B is a cross sectional view of the electrosurgical apparatus shownin FIG. 2A taken along line A-A;

FIG. 3A is an enlarged cross sectional view of the electrosurgicalapparatus in accordance with an embodiment of the present disclosure;

FIG. 3B illustrates a front view of the electrosurgical apparatus shownin FIG. 3A taken along line B-B;

FIG. 4 is an enlarged cross sectional view of the electrosurgicalapparatus shown in FIG. 3A with a blade extended;

FIG. 5 is a cross sectional view of an electrosurgical apparatus inaccordance with another embodiment of the present disclosure;

FIGS. 6A and 6B illustrate a variable structural capacitor to beemployed in an electrosurgical apparatus in accordance with anembodiment of the present disclosure;

FIGS. 7A and 7B illustrate a variable structural capacitor to beemployed in an electrosurgical apparatus in accordance with anotherembodiment of the present disclosure; and

FIG. 8 illustrates an exemplary electrosurgical apparatus including anarticulating distal end in accordance with an embodiment of the presentdisclosure.

It should be understood that the drawing(s) is for purposes ofillustrating the concepts of the disclosure and is not necessarily theonly possible configuration for illustrating the disclosure.

DETAILED DESCRIPTION

Preferred embodiments of the present disclosure will be describedhereinbelow with reference to the accompanying drawings. In thefollowing description, well-known functions or constructions are notdescribed in detail to avoid obscuring the present disclosure inunnecessary detail. In the drawings and in the description which follow,the term “proximal”, as is traditional, will refer to the end of thedevice, e.g., instrument, apparatus, applicator, handpiece, forceps,etc., which is closer to the user, while the term “distal” will refer tothe end which is further from the user. Herein, the phrase “coupled” isdefined to mean directly connected to or indirectly connected withthrough one or more intermediate components. Such intermediatecomponents may include both hardware and software based components.

FIG. 1 shows an exemplary monopolar electrosurgical system generallyindicated as 10 comprising an electrosurgical generator (ESU) generallyindicated as 12 to generate power for the electrosurgical apparatus 10and a plasma generator generally indicated as 14 to generate and apply aplasma stream 16 to a surgical site or target area 18 on a patient 20resting on a conductive plate or support surface 22. The electrosurgicalgenerator 12 includes a transformer generally indicated as 24 includinga primary and secondary coupled to an electrical source (not shown) toprovide high frequency electrical energy to the plasma generator 14.Typically, the electrosurgical generator 12 comprises an isolatedfloating potential not referenced to any potential. Thus, current flowsbetween the active and return electrodes. If the output is not isolated,but referenced to “earth”, current can flow to areas with groundpotential. If the contact surface of these areas and the patient isrelatively small, an undesirable burning can occur.

The plasma generator 14 comprises a handpiece or holder 26 having anelectrode 28 at least partially disposed within a fluid flow housing 29and coupled to the transformer 24 to receive the high frequencyelectrical energy therefrom to at least partially ionize noble gas fedto the fluid flow housing 29 of the handpiece or holder 26 to generateor create the plasma stream 16. The high frequency electrical energy isfed from the secondary of the transformer 24 through an active conductor30 to the electrode 28 (collectively active electrode) in the handpiece26 to create the plasma stream 16 for application to the surgical site18 on the patient 20. Furthermore, a current limiting capacitor 25 isprovided in series with the electrode 28 to limit the amount of currentbeing delivery to the patient 20.

The return path to the electrosurgical generator 12 is through thetissue and body fluid of the patient 20, the conductor plate or supportmember 22 and a return conductor 32 (collectively return electrode) tothe secondary of the transformer 24 to complete the isolated, floatingpotential circuit.

In another embodiment, the electrosurgical generator 12 comprises anisolated non-floating potential not referenced to any potential. Theplasma current flow back to the electrosurgical generator 12 is throughthe tissue and body fluid and the patient 20. From there, the returncurrent circuit is completed through the combined external capacitanceto the plasma generator handpiece 26, surgeon and through displacementcurrent. The capacitance is determined, among other things, by thephysical size of the patient 20. Such an electrosurgical apparatus andgenerator are described in commonly owned U.S. Pat. No. 7,316,682 toKonesky, the contents of which are hereby incorporated by reference inits entirety.

It is to be appreciated that transformer 24 may be disposed in theplasma generator handpiece 26, as will be described in variousembodiments below. In this configuration, other transformers may beprovided in the generator 12 for providing a proper voltage and currentto the transformer in the handpiece, e.g., a step-down transformer, astep-up transformer or any combination thereof.

Referring to FIG. 2A, an electrosurgical apparatus 100 in accordancewith the present disclosure is illustrated. Generally, the apparatus 100includes a housing 102 having a proximal end 103 and a distal end 105and a tube 104 having an open distal end 106 and a proximal end 108coupled to the distal end 105 of the housing 102. The housing 102includes a right side housing 110 and left side housing 112, and furtherincludes provisions for a button 114 and slider 116. Activation of theslider 116 will expose a blade 118 at the open distal end 106 of thetube 104. Activation of the button 114 will apply electrosurgical energyto the blade 118 and, in certain embodiments, enable gas flow throughthe flow tube 122, as will be described in detail below.

Additionally, a transformer 120 is provided on the proximal end 103 ofthe housing for coupling a source of radio frequency (RF) energy to theapparatus 100. By providing the transformer 120 in the apparatus 100 (asopposed to locating the transformer in the electrosurgical generator),power for the apparatus 100 develops from higher voltage and lowercurrent than that required when the transformer is located remotely inthe generator, which results in lower thermalization effects. Incontrast, a transformer back in the generator produces applicator powerat a lower voltage, higher current with greater thermalization effects.Therefore, by providing the transformer 120 in apparatus 100, collateraldamage to tissue at the operative site is minimized.

A cross section view along line A-A of the apparatus 102 is shown inFIG. 2B. Disposed within the housing 102 and tube 104 is flow tube 122which runs along the longitudinal axis of the apparatus 100. On a distalend 124 of the flow tube 122, the blade 118 is retained within the flowtube 122. A proximal end 126 of the flow tube 122 is coupled to a sourceof gas via a tube connector 128 and flexible tubing 129. The proximalend 126 of the flow tube 122 is also coupled to a source of RF energyvia plug 130 which couples to transformer 120. The flow tube 122 is madeof an electrically conducting material, preferably stainless steel, asto conduct the RF energy to the blade 118 when being employed for plasmaapplications or electrosurgical cutting as will be described below. Theouter tube 104 is constructed from non-conductive material, e.g.,Lestran. The slider 116 is coupled to the flow tube 122 via a retainingcollar 132. A printed circuit board (PCB) 134 is disposed in the housing102 and controls the application of the RF energy from the transformer120 via the button 114.

It is to be appreciated that the slider 116 may be freely moveable in alinear direction or may include a mechanism for incremental movements,e.g., a ratchet movement, to prevent an operator of the apparatus 100from over extending the blade 118. By employing a mechanism forincremental movements of the blade 118, the operator will have greatercontrol over the length of the exposed blade 118 to avoid damage totissue at the surgical site.

An enlarged view of the distal end 106 of the outer tube 104 is alsoillustrated in FIG. 2B. Here, the blade 118 is coupled to the flow tube122 which is held in place in the outer tube 104 by at least one seal136. The at least one seal 136 prevents backflow of gas into tube 104and housing 102. A cylindrical ceramic insert 138 is disposed in thedistal end of the outer tube 104 to maintain the blade along thelongitudinal axis of the apparatus 100 and provide structural supportduring mechanical cutting when the blade is exposed beyond the distalend of the outer tube 104.

The operational aspect of the apparatus 100 will now be described inrelation to FIGS. 3A and 3B, where FIG. 3A shows an enlarged crosssection of the apparatus and FIG. 3B illustrates a front view of theapparatus.

Referring to FIG. 3A, the flow tube 122 is disposed in the outer tube104 with a cylindrical insulator 140 disposed around the flow tube 122.Slider 116 is coupled to the insulator 140 and is employed to extend andretract the blade 118. At the distal end 106 of the outer tube 104, theannular or ring shaped seal 136 and cylindrical ceramic insert 138 aredisposed about the flow tube 122. As can be seen In FIG. 3B, thegenerally planar blade 118 is coupled to an inner circumference of thecylindrical flow tube 122 such that two gas passageways 142, 144 areformed on the both sides of the blade 118. As gas flows from theproximal end 103 of the housing through the flow tube 122, the gas willpass over the blade 118 out the distal end of the outer tube 104.

When the blade is in the retracted position as shown in FIG. 3A, theapparatus 102 is suitable for generating plasma. In the retractedposition, RF energy is conducted to a tip 146 of the blade 118 from anelectrosurgical generator (not shown) via the flow tube 122. An inertgas, such as helium or argon, is then supplied to the flow tube fromeither the electrosurgical generator or an external gas source. As theinert gas flows over the sharp point 146 of the blade 118 held highvoltage and high frequency, a cold plasma beam is generated.

Referring to FIG. 4, the blade 118 is advanced, via slider 116, so thetip 146 is extended pass the distal end 106 of the outer tube 104. Inthis state, the blade 118 can be used for two cutting modes: mechanicalcutting and electrosurgical cutting. In the mechanical cutting mode, RFor electrosurgical energy is not applied to the flow tube 122 or blade118, and therefore, the blade 118 is in a de-energized state. In thismode, the blade 118 can be used excise tissue via mechanical cutting.After the tissue is removed, the blade 118 may be retracted via theslider 116 and electrosurgical energy and gas may be applied via button114 to generate a cold plasma beam for cauterization, sterilizationand/or hemostasis of the operative patient site.

In the electrosurgical cutting mode, the blade 118 is advanced and usedwhile both electrically energized and with inert gas flow. Thisconfiguration resembles an electrosurgical knife approach, where theelectrosurgical energy does the cutting. However, with the addition ofthe inert gas flow, cuts made show virtually no eschar, with very littlecollateral damage along the side walls of the cut. The cutting speed isconsiderably faster, with less mechanical cutting resistance as comparedto when the knife blade is not electrically energized, i.e., themechanical cutting mode. Hemostasis is also affected during thisprocess.

In another embodiment, an electrosurgical apparatus 200 as shown in FIG.5 is configured with a structural current limiting capacitor in thedistal end of the apparatus or handpiece to limit the current applied tothe operative site of the patient. Generally, a capacitor is formed bytwo parallel conductive plates with an insulating dielectric material inbetween them. The capacitance is defined by:

C=Kε ₀(A/d)  (1)

where C is the capacitance in Farads, K is the dielectric constant(sometimes called “relative permittivity”), ε₀ is the permittivity offree space (approximately 8.854×10⁻¹² Farad/meter), A is the area of thecapacitor plates, and d is their separation distance. Some typicalvalues for dielectric constant are 1.000 for a vacuum (by definition),1.00054 for air, 3.8 for fused quartz, and 2.1 forpolytetrafluoroethylene (“Teflon”). The parallel plates of a capacitorcan take the form of concentric conductive tubes with the insulatingdielectric between them as shown In FIG. 5, and can also form astructural, as well as electrical element.

Referring to the embodiment shown in FIG. 5, the flow tube of theapparatus 200 includes a first inner flow tube 212 coupled to a second,outer flow tube 213. The inner flow tube 212 has a smaller outerdiameter than the inner diameter of the outer flow tube 213. Acylindrical insulator 240 is disposed around a distal portion of theinner flow tube 212 and then inserted into the outer flow tube 213. Asshown in FIG. 5, the inner flow tube 212 is inserted into the outer flowtube 213 approximately a distance equal to the length of the insulator240. The resulting coaxial structure 250 creates a capacitive couplingfor the inner and outer flow tubes 212, 213, where the total capacitanceis approximately equal to the capacitance of the coaxial structure 250plus the capacitance of the remaining length of outer flow tube 213. Thecoaxial structure 250 acts as a current-limiting capacitor limiting thecurrent applied to the operative site of the patient. When the slider116 is moved to either extend or retract the blade 118, the componentsof the coaxial structure 250, including the inner flow tube 212,insulator 240 and outer flow tube 213, move together as a fixed unit. Inother aspects, the operation of the embodiment shown in FIG. 5 issimilar to the embodiments described above.

In a further embodiment, the electrosurgical apparatus of the presentdisclosure will include a variable structural capacitor 350 as shown inFIG. 6. The capacitance of a structural capacitor can be varied,assuming a fixed dielectric constant K, by varying the area between theinner and outer conductive tubes. Referring to FIG. 6, inner conductivetube 312 and outer conductive tube 313 are configured to slide relativeto each other, with a sleeve of dielectric insulator 340 between themfixed to one of the inner or outer tubes 312, 313 respectively. Thedegree of overlap of the inner and outer conductive tubes 312, 313affects the resulting capacitance. In the example shown in FIG. 6A, theinsulating dielectric sleeve 340 is fixed to the inner conductive tube312. The approximately 50% overlap of the outer tube 313 over insulator340, shown in FIG. 6A, results in a relative capacitance value of “C”and 100% overlap shown in FIG. 6B, in a capacitance of “2C.”

While capacitors will block direct current, and provide protection fromgalvanic currents in an electrosurgical application, capacitors willpass alternating currents as a result of their capacitive reactance,which is defined by:

X _(C)=1/(2πfC)  (2)

where X_(C) is the capacitive reactance (in units of resistance), C isthe capacitance, and f is the frequency. Due to this inverserelationship, as the capacitance increases, the capacitive reactancedecreases. For a given applied voltage and fixed frequency, as thecapacitance increases, the amount of current limited by this capacitorwill also increase as a result of decreased capacitive reactance.

In the example shown in FIG. 6, the capacitance setting in FIG. 6Alimits the current to a lower value than the setting shown in FIG. 6B.In this embodiment, a second slider (not shown) provides the opportunityto adjust this value at the hand piece during a surgical procedure,without being interrupted to make an adjustment at the generator.

It is important to note that when adjusting the current limiting valuethrough varying the relative positions of the inner and outer conductivetubes, that other moveable components, such as the position of theretractable blade, not also be affected. One way to achieve this is witha dual slider configuration 450 as shown in FIG. 7. One side of theslider, or inner conductive tube 412, has the dielectric insulatingsleeve 440 to act as the adjustable current limiting capacitor. Theother side simply maintains electrical contact to a second outerconductive tube 442 which attaches to the retractable blade (not shown),and allows relative movement without disturbing the position of theretractable blade. This is illustrated in FIG. 7, showing a low currentlimit value on the left (FIG. 7A), and a high current limit value on theright (FIG. 7B). The position of the inner “slider” tube 412 may becontrolled manually by the surgeon via a first slider member, orautomatically by electromechanical, pneumatic or similar means. Thisprovides the opportunity to create a feedback loop where the currentlimit is self-adjusted based on a measured parameter such as absorbedpower, tissue temperature, tissue impedance or tissue type. A secondslider member may be provided and coupled to the outer tube 442 toextend and retract the blade, when the blade is coupled to the distalend of the outer tube 442.

In a further embodiment, the electrosurgical apparatus of the presentdisclosure will have an articulating distal end. Referring to FIG. 8,the electrosurgical apparatus 500 will have similar aspects to theembodiments described above with the distal end 506, e.g., approximately2 inches, being flexible to maneuver the distal end 506 at the surgicalsite. An additional control 517, e.g., a slider, trigger, or the like,is provided in the proximal housing 502 to control the bending of thedistal end 506. As in the above described embodiments, a button 514 isprovided to apply electrosurgical energy to the blade 518 and, incertain embodiment, enable gas flow through the flow tube. Furthermore,slider 516 will expose the blade 518 at the open distal end 506 uponactivation.

In one embodiment, the articulating control 517 will include two wires,one pulling to articulate and one pulling to straighten the distal end506. The outer tube 504 will be the similar to the design shown in FIG.2 and will be rigid, preferably made of Ultem™ or similar material, upto the last 2 inches which would be made of a material similar to thatof a gastrointestinal (GI) flexible scope. In certain embodiments,inside the outer tube 504 is constructed of a mesh infused Teflon™ orsimilar material and a flexible insulating material that would allow thedistal end 506 to bend at least 45° and not collapse the inner tubecarrying the gas. The blade 518 will be made of a flexible metallicmaterial such as Nitinol™ that would be able to bend but would retainit's memory in the straightened position. Alternatively, a straightmetal blade 518 would be provided with the distal 2 inches made of alinked metal such that it would still carry a current but would bebendable and the cutting portion of the blade 518 would be attached tothe distal end of the linked portion.

While the disclosure has been shown and described with reference tocertain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the disclosure asdefined by the appended claims.

Furthermore, although the foregoing text sets forth a detaileddescription of numerous embodiments, it should be understood that thelegal scope of the invention is defined by the words of the claims setforth at the end of this patent. The detailed description is to beconstrued as exemplary only and does not describe every possibleembodiment, as describing every possible embodiment would beimpractical, if not impossible. One could implement numerous alternateembodiments, using either current technology or technology developedafter the filing date of this patent, which would still fall within thescope of the claims.

It should also be understood that, unless a term is expressly defined inthis patent using the sentence “As used herein, the term ‘______’ ishereby defined to mean . . . ” or a similar sentence, there is no intentto limit the meaning of that term, either expressly or by implication,beyond its plain or ordinary meaning, and such term should not beinterpreted to be limited in scope based on any statement made in anysection of this patent (other than the language of the claims). To theextent that any term recited in the claims at the end of this patent isreferred to in this patent in a manner consistent with a single meaning,that is done for sake of clarity only so as to not confuse the reader,and it is not intended that such claim term be limited, by implicationor otherwise, to that single meaning. Finally, unless a claim element isdefined by reciting the word “means” and a function without the recitalof any structure, it is not intended that the scope of any claim elementbe interpreted based on the application of 35 U.S.C. § 112, sixthparagraph.

What is claimed is:
 1. An electrosurgical apparatus comprising: ahousing having a passage extending therethough, the housing having aproximal end and a distal end; an electrically conducting tube having aproximal end and a distal end, the electrically conducting tube beingdisposed in the passage of the housing; an insulating outer tube havinga proximal end and a distal end, the outer tube disposed around theelectrically conducting tube with the proximal end of the outer tubecoupled to the distal end of the housing, the electrically conductingtube being movable along a longitudinal axis of the housing and outertube; and an electrically conducting blade coupled to the distal end ofthe electrically conducting tube, wherein in a first position of theelectrically conducting tube, the blade extends beyond the distal end ofthe outer tube for mechanical cutting and, in a second position of theelectrically conducting tube, the blade is retracted within the outertube and is energized via the electrically conducting tube to formplasma when an inert gas flows through the electrically conducting tube,wherein the electrically conducting tube is configured as a structuralcurrent limiting capacitor to limit current applied to a operative sitewhen the electrically conducting tube is energized.
 2. Theelectrosurgical apparatus of claim 1, wherein the electricallyconducting tube includes: a first, inner flow tube having a proximal endand a distal end; a second, outer flow tube having a proximal end and adistal end; and a cylindrical insulator disposed around the distal endof the first, inner flow tube for coupling the first, inner flow tube toan inner portion of the proximal end of the second, outer flow tube,wherein an overlapping portion of the first, inner flow tube, thecylindrical insulator and the second, outer flow tube forms thestructural current limiting capacitor.
 3. The electrosurgical apparatusof claim 2, wherein at least one of the first, inner flow tube andsecond, outer flow tube is movable relative to each other to varying acapacitance value of the structural current limiting capacitor.
 4. Theelectrosurgical apparatus of claim 3, further comprising a first slidermember coupled to the first, inner flow tube for variably setting acurrent limit of the capacitor, the first slider member being accessibleon the housing.
 5. The electrosurgical apparatus of claim 4, furthercomprising a second slider member coupled to the second, outer flow tubefor extending and retracting the blade, the second slider member beingaccessible on the housing.
 6. The electrosurgical apparatus of claim 1,further comprising a slider member coupled to the electricallyconducting tube for moving the electrically conducting tube therebyextending and retracting the blade, the slider member being accessibleon the housing.
 7. The electrosurgical apparatus of claim 6, wherein theslider member includes a ratchet mechanism for incrementally moving theblade.
 8. The electrosurgical apparatus of claim 1, further comprising atransformer disposed on the proximal end of the housing, the transformercoupled to the electrically conducting tube for providingelectrosurgical energy thereto.
 9. The electrosurgical apparatus ofclaim 8, further comprising a button disposed on the housing and coupledto an output of the transformer for activating and deactivating theelectrosurgical energy to the electrically conducting tube.
 10. Theelectrosurgical apparatus of claim 1, wherein the electricallyconducting blade is generally planar and is coupled to an innercircumference of the electrically conducting tube.
 11. Anelectrosurgical apparatus comprising: a housing having a passageextending therethough, the housing having a proximal end and a distalend; an electrically conducting tube having a proximal end and a distalend, the electrically conducting tube being disposed in the passage ofthe housing; an insulating outer tube having a proximal end and a distalend, the outer tube disposed around the electrically conducting tubewith the proximal end of the outer tube coupled to the distal end of thehousing, the electrically conducting tube being movable along alongitudinal axis of the housing and outer tube; and an electricallyconducting blade coupled to the distal end of the electricallyconducting tube, wherein in a first position of the electricallyconducting tube, the blade extends beyond the distal end of the outertube for mechanical cutting and, in a second position of theelectrically conducting tube, the blade is retracted within the outertube and is energized via the electrically conducting tube to formplasma when an inert gas flows through the electrically conducting tube,wherein the electrically conducting tube and the insulating outer tubeare configured to articulate at their respective distal ends.
 12. Anelectrosurgical apparatus of claim 11, wherein the electricallyconducting tube is configured from a conductive mesh.
 13. Theelectrosurgical apparatus of claim 11, wherein the electricallyconducting blade is configured from a flexible material to articulatewith the electrically conducting tube and the insulating outer tube. 14.The electrosurgical apparatus of claim 11, wherein the electricallyconducting blade is configured from at least two linked members toarticulate with the electrically conducting tube and the insulatingouter tube.
 15. The electrosurgical apparatus of claim 11, furthercomprising a slider member coupled to the electrically conducting tubefor moving the electrically conducting tube thereby extending andretracting the blade, the slider member being accessible on the housing.16. The electrosurgical apparatus of claim 15, wherein the slider memberincludes a ratchet mechanism for incrementally moving the blade.
 17. Theelectrosurgical apparatus of claim 11, further comprising a transformerdisposed on the proximal end of the housing, the transformer coupled tothe electrically conducting tube for providing electrosurgical energythereto.
 18. The electrosurgical apparatus of claim 17, furthercomprising a button disposed on the housing and coupled to an output ofthe transformer for activating and deactivating the electrosurgicalenergy to the electrically conducting tube.
 19. The electrosurgicalapparatus of claim 11, wherein the electrically conducting blade isgenerally planar and is coupled to an inner circumference of theelectrically conducting tube.
 20. The electrosurgical apparatus of claim11, wherein the electrically conducting tube is configured as astructural current limiting capacitor to limit current applied to aoperative site when the electrically conducting tube is energized.